Ink jet printers require an ink supply to be in fluid contact with an ink drop ejecting device which precisely ejects ink onto a recording media. The ink supply must be maintained at a relatively constant pressure to keep the ink from discharging from the ejecting device at the wrong time or in an undesired amount. There are several methods and devices for maintaining a constant negative back-pressure including capillary fibers or foam, bladder-type configurations and lung-type configurations.
Bladder and lung configurations may consist of a rigid frame with either one or two side panels made of a thin plastic laminate material. Both configurations depend on a flexing of the side panels which is resisted by a biasing member located either between the side panels (bladder configurations) or between one of the side panels and a rigid panel attached to the frame (lung configurations). The resistance of the biasing member is predictable and linear as it compresses and expands. However, the thin film side panels often contain wrinkles which are of random size and distribution which ultimately make the system behavior erratic and unpredictable.
A previously used method of attaching the side panels to a frame was to place the flat laminate material on the bladder frame and use a shim to depress the material some distance into the frame interior as the laminate material was being heated in order to conform the web to a cavity defined by the frame. The side panels were then heat sealed to the frame perimeter, allowing the spring to flex through a specified range of motion. This method had the undesirable effect of introducing wrinkles into the topology of the side panels.
Wrinkles or irregularities of the side panels result in sub-optimal performance characteristics such as hysteresis and erratic back-pressure/volume relationships in the ink reservoir. This erratic behavior translates into large back-pressure fluctuations during operation which can affect ink spot size, and/or timing and, ultimately, print quality. Furthermore, these problems are exacerbated in a refillable reservoir design in which the bladder spring is used both as a back-pressure device as well as a pump to refill the reservoir with ink. Hysteresis and back-pressure fluctuations can prevent the ink cartridge from being completely or reproducibly refilled with ink. What is needed, therefore, is an apparatus and a manufacturing method for the apparatus, which enables predictable and consistent back-pressure on the ink supply during use.